This invention relates to decorative molded foams which exhibit good impact resistance and good fire retardant properties. This invention also relates to a process for preparing these decorative molded foams. The molded foams of the present invention are flexible and have a medium density, i.e. the density ranges from about 10 to about 30 pounds per cubic foot (pcf). These foams are suitable for use as building materials in the construction industry.
Polyurethane foams are used for a wide variety of applications, such as thermal insulation, packaging, upholstery, carpet underlay, automobile dashboards, building materials, and structural material. An important factor to be considered in employing polyurethane or other polymeric foams is the ability of such foams to resist ignition, or once ignited, to be self-extinguishing after the ignition source is removed. This factor becomes even more important if the foam is to be used within a confined space or in fire-prone outdoor locations.
As those skilled in the art are aware, the most common method of decreasing the flammability of polyurethane foams is by incorporating a flame retarding agent, such as a halogen- or phosphorus-containing compound, into the foam formulation. Although such compounds provide good improvement in the flame retardation properties, relatively large quantities of these agents may have to be employed to obtain satisfactory results in more severe tests. Incorporating large quantities of these agents into polyurethane foams usually results in loss of impact strength and flexibility.
For many years, the dominant blowing agents used to expand polyurethane foam had been the cholorfluorocarbons. These blowing agents were phased out after having been determined to pose a threat to stratospheric ozone. After the cholorfluorocarbons were phased out, the most common class of blowing agents became the hydrogenated chlorofluorocarbons. Although these are considered to be somewhat more environmentally friendly expansion agents, the hydrogenated chlorofluorocarbons still contain some chlorine. The chlorine atoms of hydrogenated chlorofluorocarbons are stable at altitudes under the stratosphere, and thus have a lower ozone-depleting potential (“ODP”). However, because of the hydrogenated chlorofluorocarbons still have a small ODP, they have also been mandated for eventual phase out. Water and/or carbon dioxide are rapidly becoming the blowing agents of choice for polyurethane foam manufacturers.
As described in U.S. Pat. Nos. 4,797,428 and 4,940,632, there are some polyurethane foams available that pass the ASTM E84 Tunnel Test “Standard Test Method for Surface Burning Characteristics of Building Materials” (ASTM International) with a Class I rating. These foams use the alternative chlorofluorocarbon/hydrogenated chlorofluorocarbon blowing agents in combination with highly loaded polyester polyol blends and liquid flame retardants or have high flame retardant filler loadings, including phosphorus-based materials, in combination with trimethylolpropane-based polyols to produce the desired end result. These polyester-containing foams tend to reduce long term hydrolytic and “creep” stability and thus are not suitable for applications outside of insulation-type foams. These insulation foams normally have density less than 4 pcf and are brittle with little or no impact resistance.
U.S. Pat. No. 5,086,084 discloses a foamed polymeric material suitable as a wood substitute, made of a continuous phase of polyurethane having solid polyvinyl chloride particles dispersed therein. The wood-like material of this reference contains about 100 parts of a foamable urethane, and 10 to 50 parts polyvinyl chloride (PVC) particles having a particle size below 200 μm. This material has a microcellular structure with cells on the order of 0.1 mm in average diameter or less. The walls are said to be made of a matrix of polyurethane reinforced with PVC particles. There is no discussion of the flame resistant performance properties of these polymeric materials.
Water-blown, flame retardant rigid polyurethane foams which satisfy the requirements of ASTM E-84 for Class I materials are disclosed in U.S. Published Patent Application 2007/0129452. These rigid foams are the reaction product of at least one polyisocyanate, with a polyol component that contains from 2 to 35 wt. % of at least one sucrose based polyol, from 2 to 35 wt. % of at least one non-sucrose based isocyanate-reactive component, and from 1 to 13 wt. % of at least one aromatic polyester polyol, in the presence of water, optionally at least one of carbon dioxide, surfactants, flame retardants, pigments, and catalysts and fillers. These foams do not contain any trimethylolpropane based polyols.
Finally, flame-proofed thermoplastic molding compounds are disclosed in U.S. Published Patent Application 2004/0176510. These are the reaction product of A) from 10 to 97% by weight of at least one polyester, B) from 1 to 30% by weight of flame-retardant component, C) from 0.01 to 5% by weight of KH2PO4 or LiH2PO4, and E) from 0 to 70% by weight of other additives, with the sum of the percentages of A) through E) totaling 100% by weight. Suitable polyesters include polyethylene terephthalate (PET) and at least one polyester other than polyethylene terephthalate (PET). Up to 30 mol % of the dicarboxylic acids used to prepare the non-PET polyester can be adipic acid. The halogen-containing flame retardant contains 1 to 30% by weight of a halogen-containing flame-retardant, and from 1 to 80% by weight of an antimony oxide. This reference does not, however, mention flexible molded polyurethane foams.
Thus, there continues to be a need for flexible molded polyurethane foams which have good impact strength and good fire retardant properties. It is also desirable that such foams would use non chlorofluorocarbon/hydrogenated chlorofluorocarbon-containing blowing agents, such as water and/or carbon dioxide.